TAO_IDL Wide Char Literal Escapes

[iguessthislldo]

While testing that the IDL I wrote for this PR was correct, I found that there is TAO_IDL can't compile wide character literals with escapes in them:

const wchar m = L'i';
const wchar n = L'\n';
const wchar o = L'\'';

Running it results in:

Error - tao_idl: "wide_char_issue.idl", line 2: error in lookup of symbol: L
tao_idl: wide_char_issue.idl: found 1 error

Commenting out n line results in:

syntax error
Error - tao_idl: "wide_char_issue.idl", line 3: Malformed const declaration

Commenting out o line, results in success.

Besides isolating the issues, I haven't look into this further, but I suspect that escapes aren't properly implemented for wide character literals, or perhaps are not implemented all.

[jwillemsen]

This looks legal IDL to me, it is accepted by ridlc

[iguessthislldo]

Some additional info: While testing C++11 character literals in OpenDDS, I noticed that it does accept the 'u' escape:

const wchar c = L'\u203C';

Which allows our C++11 mapping to work after I updated it to print char literals correctly:

constexpr wchar_t c = L'\x203c';

tao_idl silently emits invalid C++:

const CORBA::WChar c = L';